1. Field of the Invention
The present invention relates to a method for displaying the measurement conditions on a measurement device. More specifically, the invention relates to the display of information related to error correction, namely, the correction conditions. The display method of the present invention is suited for use in a measurement device equipped with a plurality of ports.
2. Discussion of the Related Art
A measurement device is rarely in the ideal state for the entire apparatus and generally differences develop between the measurements and the true values. These differences, namely the causes of the measurement errors, have reproducibility and predictability over some time span or some temperature range. The measurement errors based on these causes can be removed and the measurement device is calibrated. In order to remove these measurement errors, a network analyzer, which is a measurement device, is calibrated based on measurements such as the thru, open, short, and high-precision load impedance, which are well-known electrical standards. Thus, the network analyzer can correct the measurements and display measurement results close to the true values.
A network analyzer has calibration methods such as response calibration and full N-port calibration, where N is a natural number. Each calibration method has various features such as the measurement accuracy and the measurement time. The user adopts a calibration method while considering these features. It would be convenient if the user could determine how to error correct the S-parameters during the measurement, that is, how to measure the measurement errors of the S-parameters beforehand by some calibration method and correct the measurements, because the user can judge whether or not the values of the S-parameters to be measured are valid. Therefore, a conventional network analyzer has a function to display various calibration methods applied to the S-parameters to be measured on the screen for displaying the measurement results.
FIG. 1 is a front view of a conventional network analyzer. In FIG. 1, the network analyzer 100 is a 3-port network analyzer equipped with ports A, B, and C for connecting to the device under test α (not shown) and measuring the reflection coefficient and propagation coefficient and a screen 110 for displaying the measurement conditions and the measurement results.
The trace 120, which is an S-parameter measurement, and the symbol 130 indicating the correction method are displayed on the screen 110.
The symbol 130 is “C1” when the measured S-parameters are corrected by response calibration or full 1-port calibration, “C2” when corrected by full 2-port calibration, and “C3” when corrected by full 3-port calibration. Consequently, if symbol 130 displays “C2” as shown in FIG. 1, the user can know that the S-parameters are corrected by full 2-port calibration during measurement. If the user cannot connect the device under test to two ports and cannot conduct the measurements, correct error correction is not performed.
However, the displayed calibration method is only a simple symbol display, which is inconvenient when the ports used during measurement are specified. This inconvenience is obvious when an unspecified number of users share the network analyzer.
For example, when the network analyzer 100 in this example is used and the reflection coefficient S22 is measured at port B, whether the combination of measurement ports targeted by full 2-port calibration is the port B and port A group or the port B and port C group cannot be determined by only knowing the symbol 130. Thus, if which ports were used and what kind of calibration method was applied cannot be determined during calibration, the user must verify the calibration methods of the other S-parameters and must specify the port group that should be used in the measurements. When using a conventional network analyzer, the traces of the S-parameters must be displayed in order to verify the calibration methods for the S-parameters, which is a nuisance. In addition, this specification task becomes complex as the number of ports of the network analyzer becomes large. When a plurality of calibration methods coexists and is applied, this task is extremely difficult.
Therefore, the network analyzer should provide a method that easily determines information related to the error correction of the S-parameters, that is, the correction conditions.